graceful degradation
fault tolerance
https://source.unsplash.com/featured/?graceful-degradation#.png
/suto3/google.icongraceful degradation
/suto3/Google画像検索.icongraceful degradation
/suto3/Google定義検索.icon graceful degradation
/suto3/wikipedia.icongraceful degradation
/suto3/weblio.icon graceful degradation
/suto3/kotobank.icon graceful degradation
/suto3/jisho.icon graceful degradation